This invention relates to a shredding device, comprising a driving unit for driving at least one rotor having shredding tools on its periphery which for shredding material to be comminuted, for instance waste material and/or production residues, interact with at least one counter knife assembly that is arranged in a stationary manner with respect to the machine housing of the device during the shredding operation. The invention also relates to a process for operating such a shredding device.
Such shredding devices are used for instance for comminuting wood, paper, plastics, rubber, textiles, production residues or waste material from industry and commerce but also bulky waste, domestic refuse, paper and DSD (Duales System Deutschland=German dual system) collections such as hospital waste etc. The material to be processed is shredded by a cutting, shearing, crushing, tearing and/or grinding operation of the rotor cooperating with its associated stationary counter knife assembly. A device of this type is described for example in patents EP 0 419 919 B1 and DE 103 33 359 B3.
Normally, the counter knife assembly is adapted in its design to the surface of revolution of the shredder shaft for comminuting the shredding material, which surface of revolution is determined by the shredding tools. If the shredding tools have for instance a tooth structure, the counter knife assembly may have a complementary tooth structure of the counter knives in such a manner that the teeth of the rotary tool mesh with the teeth of the counter knives during the shredding process. The clearance between the shredding tools and the counter knife assembly is a decisive factor for the shredding operation, particularly if the material to be comminuted includes thin constituent parts such as films or textiles.
In the course of operation of the device, both the shredding tools and the counter knife assembly, in the described example the counter knife teeth interacting with the shredding tools, will become worn. For this reason, the shredding tools and the counter knives must be regularly exchanged. Known by prior art is also a counter knife assembly including a knife bar which after a predetermined operation time or in response to a predetermined wear, is radially displaced toward the rotor in order to reduce the gap between the wearing shredding tools and the wearing counter knife during a maintenance period in which no processing of shredding material takes place. In cases in which both the shredding tools and the counter knife assembly have a tooth structure, the teeth and particularly the teeth flanks will not wear symmetrically, so that as a result the clearance cannot be uniformly reduced over the entire tooth structure by the displacement of the counter knife assembly toward the rotor. Instead, with an increasing wear, the gaps remaining between the teeth of the rotor tools and the counter knives become increasingly large, even if the counter knife assembly is advanced as far as to contact the shredding tools. Especially in cases in which the material to be processed includes also films and textiles, the tools or the counter knives must be exchanged in order to again provide for the required clearance which is sufficiently narrow for comminuting even such materials. Operational availability of the device is considerably limited by the exchange of these shredding means.